The present application relates generally to the field of sawing lumber into planks and, more particularly, to an improved work piece hold down apparatus for feeding lumber stock of varying thickness into a horizontal bandsaw.
Shipping pallets provide a flat surface for supporting goods stacked thereon in an elevated position suitable for lifting by a forklift. It is estimated that there are over two billion pallets in use in the United States and that roughly one-half billion new pallets per year are needed. This demand drives the need for machines capable of producing the necessary quantity of planks suitable for pallet construction.
One such machine for producing rough planks for pallet construction incorporates a pair of generally horizontal band saw blades arranged in series along a feed path. Work pieces of varying thickness and length are fed in series along the feed path. As the work pieces reach the saw, the first bandsaw longitudinally cuts a portion of the work piece into a thick plank having a thickness roughly twice that of the desired thickness. The second bandsaw then cuts the thick plank in half longitudinally resulting in a pair of planks of the desired thickness. Any excess thickness of the feed stock extending above the first cut is re-circulated in the machine and fed through again until no more planks of the desired thickness can be cut from the feed stock.
One or more work piece hold down mechanisms is provided in the feed path to maintain the work piece firmly against the base to assure uniform thickness of the planks. These hold down mechanism are typically in the form of a wheel that rides along the top of the work piece as it travels along the feed path that is spring biased to press the work piece against the base. The mechanisms are generally positioned just upstream of the bandsaw blades. Problems arise as work pieces of different thickness are sequentially fed. Known hold down wheels lose contact with the work piece of lesser thickness as the hold down wheel steps up or down to the piece of greater thickness. During this transition, the work piece of lesser thickness is not firmly pressed against the base which can result in the plank thickness being less than desired. The thickness deviations can be large enough to render the plank unusable.
It would be advantageous to provide an improved hold down mechanism that would overcome these disadvantages and improve production efficiency.